- From: Tom Hume <tom.hume@futureplatforms.com>
- Date: Thu, 28 May 2009 08:38:19 +0100
- To: John Hardi <john.hardi@motricity.com>
- Cc: Magnus Lönnroth <magnus.lonnroth@ericsson.com>, Luca Passani <passani@eunet.no>, Mobile Web Best Practices Working Group WG <public-bpwg@w3.org>
- Message-ID: <a293dbd10905280038g61b1e00alfd3ff15320fdfc71@mail.gmail.com>
John Do you have some example code for this sort of thing, or can you point me at some? Tom 2009/5/27 John Hardi <john.hardi@motricity.com> > Tom, > > From a CP POV, one would use it to improve performance of pages which have > a number of frequently changing dynamic content parts (i.e. images). > > By using the absolute URI/URL of a resource for the Content-Location header > URI of its part , you shouldn’t need to change the references in the base > (X)HTML part. This allows a packaging filter on the front of your web > server’s page processing to handle it in a fairly generic fashion. In > general, I think this is consistent with RFC 2557. As for support, it’s > fairly broad — certainly more broad than CSS2, though that hopefully won’t > remain the case. > > John > > On 5/27/09 12:46 PM, "Tom Hume" <tom.hume@futureplatforms.com> wrote: > > John > > How, from a content provider POV, does one make use of this? How would I > refer to a specific resource within a multi-part/mixed response - using some > sort of URL scheme? And how well supported is this, in your opinion? > > Tom > > 2009/5/27 John Hardi <john.hardi@motricity.com> > > Magnus & Tom, > > While not a regular contributor, I did want to add a bit of perspective on > this topic. > > First I must concur with Magnus that MIME multipart is still in use and can > improve the user’s experience in page load times as a round-trip latency > reduction tool. While it can be a network optimization as Magnus describes, > the benefit is actually greater if done at the page source, thus eliminating > the multiple round trip latencies between the mobile network gateway / proxy > and the CP as well as from the handset across the mobile network. > > Sprites / Composite images are not comparable; they only offer improvement > for static, decorative images. If the multiple images/parts of a page are > dynamic content (news photos, album art, etc.) multipart still provides > benefit where sprites would not. It also provides the delivery performance > benefits of embedded CSS with the flexibility of a linked style sheet. > > Being a content type, use of multipart is independent of Content-Encoding. > So it’s not required that multipart payloads be gzipped, though doing so > may be worthwhile where it is also supported by the device. > > There are cases, as Luca describes, where devices advertise support in HTTP > headers but don’t necessarily handle it well. So device awareness and the > ability to override the devices’ claim of support is necessary. However, I > don’t believe this is significantly different from other advertised device / > browser capabilities (CSS2 positioning, for example). > > The degree of difficulty may make multipart debatable as a best practice, > but I don’t consider it irrelevant “from the content provider’s point of > view”. > > Hope this helps... > > John Hardi > Dir, Technology Strategy > Motricity, Inc. > > > On 5/27/09 12:22 AM, "Magnus Lönnroth" <magnus.lonnroth@ericsson.com < > http://magnus.lonnroth@ericsson.com> > wrote: > > Yes, I'm referring to HTTP responses. A proxy is needed. URL-rewriting is > needed. I'm not sure if the context for my response was appropriate - I was > just reacting to the previous statements saying that packaging content in > multi-part MIME digests was kind of obsolete. From the content provider's > point of view MIME multi-part digests are irrelevant and have probably > always been so. From the service provider's point of view it's still an > important network level optimization. But it should be completely > transparent and hence most likely not part of a best practices discussion. > Sorry if I'm confusing matters. > > /Magnus > > > > ------------------------------ > *From:* Tom Hume [mailto:tom.hume@futureplatforms.com<tom.hume@futureplatforms.com>] > > *Sent:* Wednesday, May 27, 2009 8:51 AM > *To:* Magnus Lönnroth > *Cc:* Luca Passani; Mobile Web Best Practices Working Group WG > *Subject:* Re: ACTION-961: usefulness of multipart-mixed > > > Magnus > > > Are you referring to using multi-part/mixed for HTTP responses from a web > server? > > > > If so, can you explain how resources within a multi-part/mixed HTTP > response are referred to from each other, or from outside the response? > > > > Tom > > > 2009/5/27 Magnus Lönnroth <magnus.lonnroth@ericsson.com < > http://magnus.lonnroth@ericsson.com> > > > > Hi, delivering multi-part MIME digests has been and still is an important > part of optimizing performance in our installations. The main reason for > developing this is the latency in 3g networks compared to wired broadband > or wi-fi. It must of course be fully transparent and not affect content or > content design in any way. One important aspect is to have detailed > knowledge of the device's own caching capabilities and support for digests > so that subsequent deliveries not include content that is already available > (cached) on the handset. If full digests are delivered with each request I > agree that the benefit is questionable. But if you have a good > implementation with device knowledge the improvement is significant. > > thanks, > > Magnus Lönnroth > Head of Development > Service Delivery & Provisioning, Ericsson /// > > > > > > -----Original Message----- > > From: public-bpwg-request@w3.org <http://public-bpwg-request@w3.org> > > [mailto:public-bpwg-request@w3.org <public-bpwg-request@w3.org>] On > Behalf Of Luca Passani > > Sent: Tuesday, May 26, 2009 11:49 PM > > To: Mobile Web Best Practices Working Group WG > > Subject: Re: ACTION-961: usefulness of multipart-mixed > > > > > > Multipart was a useful mechanism to deliver a full page in one shot. > > Vodafone leveraged multipart for its vodafone live service on > > devices which supported it. Multipart allowed for snappy (or at least > > "2002-snappy") display of the top page, which looked great as > > compared to everything WAP had represented until that day. > > There was no way to know whether multipart was properly > > supported by a device, except testing on that device. > > Notably, many devices declared multipart support in headers > > and UAProfs, but the information was not reliable at all. I > > recall that I never managed to get multipart to work on a > > Nokia device (still vaguely curious about whether there was a way). > > Vodafone maintained its own db with this info for devices in > > its portfolio. Not sure if they still do. Probably not. Too > > much effort for too little value. > > > > 3G networks and faster browsers make the use of multipart > > much less relevant, particularly because pages become much > > harder to build and maintain if multipart is in the middle. I > > made space for multipart in WURFL back in 2003, but the > > community did not really follow: nobody was using it obviously. > > > > Luca > > > > Tom Hume wrote: > > > I took an action a couple of weeks ago to look into multipart/mixed > > > MIME types, to see if they might be usefully related to > > sections 3.4.6 > > > and 3.4.7 of MWABP[1] (ACTION-961). In particular it would seem > > > helpful to be able to bundle many images up into a single HTTP > > > request, avoiding unnecessary round trips to download a set > > of them. > > > The current advice is to combine related images into a single file, > > > download this, and use CSS positioning and clipping to > > render parts of > > > this file. multipart/mixed would provide another route for > > downloading > > > many resources at once. > > > > > > The only reference I can find to mobile usage of multipart-mixed is > > > this tutorial from OpenWave: > > > > > > > > http://developer.openwave.com/dvl/support/documentation/technical_note > > > s/multipart.htm > > > > > > From running this experiment with desktop browsers, multipart-mixed > > > doesn't seem to be well supported. I've set up an HTTP response > > > matching the above and found that: > > > > > > - Firefox and Opera render the second page in the message > > > - Safari doesn't recognise it as HTML and downloads it > > > - IE renders content from both pages > > > > > > I've also got a question of how, from within CSS or similar, an > > > individual part of a multipart-mixed message might be uniquely > > > referred. The only reference I can find for a URL-scheme for such > > > things is a scheme for references to body parts of messages, which > > > date back to 1997 or earlier, and seem to be designed with > > HTML email > > > in mind: > > > http://www.ietf.org/rfc/rfc2392.txt > > > > > > Beyond the Openwave tutorial, and the following tool which > > exists to > > > create these messages: > > > > > > http://www.umts-tools.org/docs/multipart/ > > > > > > ...I can't find any other reference to them; and it's not a > > technique > > > I've come across myself. Am I missing something obvious here? From > > > where I'm sitting this looks like a barely-used, poorly- supported > > > technique which I'd hesitate to consider a best practice - > > though it > > > might be handy if it worked. > > > > > > Tom > > > > > > [1] http://www.w3.org/TR/2009/WD-mwabp-20090507/#d1e8981 > > > > > > -- > > > Future Platforms: hungry and foolish since 2000 > > > work: Tom.Hume@futureplatforms.com < > http://Tom.Hume@futureplatforms.com> > > > <mailto:Tom.Hume@futureplatforms.com <Tom.Hume@futureplatforms.com>> > play: tomhume.org <http://tomhume.org> <http://tomhume.org> > > > <http://tomhume.org> > > > > > > > > > > > > > > > > > > -- Future Platforms: hungry and foolish since 2000 work: Tom.Hume@futureplatforms.com play: tomhume.org
Received on Thursday, 28 May 2009 07:39:15 UTC